With the development of the TFT (thin film transistor) crystal liquid display technology, the TFT display devices based on the LTPS (Low Temperature Poly-silicon) technology have become increasingly the mainstream in the mark due to characters such as low power consuming, high resolution, quick response speed, and high aperture ratio. Such kind of display devices have been widely applied in various electric appliances, for example, digital electronic devices such as liquid crystal televisions, smart phones, tablet computers and digital cameras.
However, among the products with high resolution such as the TFT display devices based on LTPS technology, as the product resolution and the aperture ratio become higher and higher, the pixel pitch in the array substrate of an LTPS TFT display device becomes smaller and smaller, and thus the storage capacitance of the array substrate become less and less. For an LTPS TFT array substrate, given the same leakage current, the smaller the storage capacitance is, the lower the maintenance ratio of pixel voltages is, which results in occurrence of the unfavorable phenomenon such as flicker, etc. and greatly impairs the quality of an array substrate and a product with high resolution such as a TFT display device. Therefore, it is desired to increase the storage capacitance without influencing the aperture ratio of an array substrate.